A 12-year-old Berkshire girl has been given a reprimand for wasting police time after falsely reporting a rape.
The girl, from Reading, told officers she had been raped by a 15-year-old boy on 11 July.
They arrested the teenager but further inquiries showed the rape accusation was false and he was later released without charge.
Police said the investigation cost thousands of pounds and caused distress to the innocent victim.
Det Con Pauline Foy, of Thames Valley Police, said: "We take every single report of sexual assault extremely seriously and would not want to discourage anyone from coming forward to report a legitimate incident.
"However, if people falsely report incidents to police we will take appropriate action.
"In this case a 15-year-old boy was arrested as part of the initial investigation, which was obviously very distressing for him.
"Each report of sexual assault is dealt with by detectives and other specialist officers, who conduct a full investigation at great public expense.
"Forensic submissions alone can cost many thousands of pounds and together with officers' time, the investigation of any false or malicious allegation results in valuable resources not being able to address genuine issues elsewhere."